The Stage reports today, a touch hysterically, on theatre producers facing a "catastrophic" shortfall in revenue from September this year. Schools are, reportedly, cancelling theatre trips thanks to the "rarely cover" rule, which will be enforced by the Department of Children, Schools and Families on 1 September. Who's to blame? Pesky policy wonks, apparently.

Rarely cover, as the DCSF explain it, has been implemented to ensure schools provide adequate teaching cover to make up for staff absent on school trips. In essence, schools must employ substitute teachers or supervisors ("costing around £30 per hour," shrieks the Stage) for each of the multiple teachers needed to herd classes of excitable teens across the West End. The days of doling out cover lessons among existing school staff, it seems, are numbered.

School trips do, of course, make up a large chunk of the change made from matinee shows of West End productions, and the idea that attendance will be threatened by government policy has producers – not to mention theatre outreach and education programmers – in an understandable huff. A number of teachers (my own former favourite, Malcolm Ellison from Stanground college in Peterborough included) have already pointed out that the cost of organising a theatre trip under rarely cover rules would make the outing untenable. At least for the ones organised during school-time anyway.

Neal Foster, manager of Birmingham Stage Company, which is currently producing a national tour of Skellig, says in the Stage that three trips have already been cancelled due to rarely cover. But the National Theatre haven't chalked up any losses to date, and the Manchester Royal Exchange have told us there has simply been a significant increase in queries for schools having to plan many more months in advance.

But are theatremakers really the biggest losers here? No, of course: it's the students. There's little in point trying to inspire a 14-year-old with Shakespeare, Arthur Miller or JB Priestley without offering the chance to see a play in the context it's supposed to be in: at the theatre, drinking in the drama with friends. Which brings me to the other valuable lesson school theatre trips provide students – the opportunity to visit an actual theatre.

Without the insistence of my English teachers ferrying out our class to see the RSC or the National attempt a musical, I would probably have spent most of my teenage years believing that Russian literature and French pop were my lot as far as high culture was concerned. By its nature, theatre has always been less accessible than music and film. Unlike literature, it also needs to be organised (preferably with subsidised tickets) if it's going to happen at all.

Producers of major playhouses will fret at falling ticket sales, but one of the real sticking points here is the extra pressure on school staff. School theatre trips can (and will) still take place in the evenings, but it's unfair to the teachers, for whom the rule was presumably implemented to protect from bigger workloads. More than that though, it is the classes of young people – theatre's future audiences – who will be denied that first introduction to an art form they might not otherwise experience.